1. Field of the Invention
The present invention relates to a discharge apparatus with a metered dose valve for metered discharge of a pressurized liquid, wherein the metered dose valve has a valve element and a metering chamber with an associated inlet valve and an associated outlet valve, wherein the outlet valve is closed and the inlet valve is open in a first position of the valve element so that the liquid can fill the metering chamber with a metered dose, and wherein the outlet valve is open and the inlet valve is closed in a second position of the valve element so that the liquid is discharged from the metering chamber to the atmosphere
2. Description of Related Art
In particular, the present invention deals with a discharge device with a metered dose valve for use with pressurized aerosol packs, containers or the like, where a liquid product is pressurized by a liquefied or compressed gas or a solid product is suspended in a liquefied gas but is not limited to such packs.
Many pressurized aerosol packs contain a metered dose valve that accurately measures a single dose of the product within the pressurized reservoir. Such valves are used in many applications including, for example, for delivering accurate amounts of a drug to a patient or animal. Generally, the metered dose valve dispenses the total dose when it is opened with the user having no control over how much of the metered dose is delivered. In most cases, this is an important aspect of the valve as, for instance, in the case of medical inhalers, it is important that the patient receives no less or no more than the appropriate metered dose. Generally, such metered dose valves are operated by depressing an actuator, with finger pressure with the movement stopping only when the open position is reached. The metered dose valve is generally spring loaded so that it returns to the closed position when finger pressure is released. The majority of such metered dose valves contain an inlet valve and an outlet valve, usually with cut gaskets. The inlet valve connects the canister liquid reservoir with the liquid to a metering chamber while the outlet valve connects the metering chamber to the atmosphere.
When such valves are actuated by the user, the user is only aware of two positions; closed and open or first and second. In the first position, the inlet valve is open and the outlet valve is closed. In the second position, the inlet valve is closed and the outlet valve is open. When, in the first position, the metering chamber is maintained full of liquid and sealed from the atmosphere, and when in the second position the content of the metering chamber is allowed to flow into the atmosphere while the metering chamber is sealed from the liquid pressurized canister or reservoir.
On the way from the first position to the second position and vice versa, an intermediate position is passed, but the user has no knowledge of this. What the user is unaware of is that there is the intermediate position where both the inlet valve and the outlet valve are closed. This is because to accurately meter the product, i.e., the liquid, the inlet valve must be closed before the outlet valve is opened.